Consider the following data for Magnimus Corporation.

July August September Sales in units 4,800 5,800 6,400 Sales revenue $ 456,000 $ 551,000 $ 608,000 Direct materials 89,760 108,460 119,680 Direct labour 107,760 130,210 143,680 Manufacturing overhead 59,080 67,080 71,880 Sales commission 38,400 46,400 51,200 Other selling expenses 40,820 43,820 45,620 Administrative expenses 33,550 33,550 33,550

Required: Write the cost equation for direct materials. (Round your answer to 2 decimal places.)